Very high energy (\(>10\)  TeV) neutrinos of non-atmospheric origin have been observed in the last decade with the IceCube detector [1]}, [2]}, [3]}, [4]}, [5]}, [6]}. They are believed to be produced in the astrophysical sources where the ultra-high energy cosmic rays (CRs) are accelerated, through the interactions of these with the gas or the radiation present in the acceleration sites or their surroundings. These interactions can produce unstable particles, mostly pions, which through their weak decays give rise to neutrinos, with the decays of the neutral pions giving rise to comparable amounts of gamma rays (for recent reviews see [7]}, [8]}). Also the interactions of the CRs with the background radiation that they traverse as they propagate through the Universe, such as the cosmic microwave background (CMB) and the extragalactic background light (EBL), can give rise to high-energy cosmogenic neutrinos [9]}. Cosmogenic neutrinos are however likely subdominant with respect to the astrophysical ones produced at the sources, except eventually at energies well beyond 10 PeV [10]}. In spite of the major progress being done, the sources of the observed neutrinos are however still largely uncertain, with only one or two potential identifications having been done up to now through the coincidence between the arrival directions of well determined muon neutrino induced tracks and the location of the blazar TXS-0506+056 [11]} or the Seyfert active galaxy NGC 1068 [3]}. The lack of correlations with source candidates of the remaining several tens of astrophysical neutrinos is also a relevant piece of the puzzle.
